屋久島におけるオキナワキノボリトカゲ対策/Measures Against the Okinawa Tree Lizard on Yakushima Island

屋久島で捕獲したオキナワキノボリトカゲのオス成体。An adult male Okinawa tree lizard captured on Yakushima.

琉球ネイチャーポジティブでは、新たな外来種の対策に取り組むこととなりました。

場所は北琉球の屋久島。

そして、対象はオキナワキノボリトカゲ Diploderum polygonatum polygonatumです。

オキナワという名前を冠するこのトカゲは、琉球ネイチャーポジティブが拠点とする沖縄島では在来種。

中琉球を象徴する生き物のひとつでありながら、開発や外来種の影響で近年その数を減らしているとされています。

それが、人の手によって屋久島を含む九州、静岡に運ばれ、逆に地域の生態系を脅かす外来種として防除対象となっているのは本当に皮肉な話。

それに加えて、ヤエヤママドボタルと同様に、このオキナワキノボリトカゲ問題には、制度的な対応の難しさも伴います。

環境省が所管する外来生物法の規制対象生物はあくまで国外からきたもの。

ヤエヤママドボタルやオキナワキノボリトカゲといった国内由来の外来種は、その影響の大小にかかわらず外来生物法の外にこぼれ落ちてしまいます。

そして、地方自治体が条例で指定しても、自前で対策するには割ける予算も人員も限られ、またその実効性もまちまちなのが現実。。。

生物の人為的移動による影響は、国境をまたぐことの有無で測れません。

近接した島間で高い固有性が保たれている生物ほど、その境界を超えたときの影響には注意が必要だと感じます。

取り返しがつかなくなってから焦る、そして諦めるのではなく、早い段階から、想像力を働かせて先手を打つ。

個人レベルから制度レベルまで、外来種対策にはとても大事な視点です。

現制度の溝も、こうした視点で運用や改善の道を探せると良いなぁ。と。

Ryukyu Nature Positive has started a countermeasure project for a new invasive species.

The next target place is Yakushima Island, located in the Northern Ryukyu.

The target species is the Okinawa tree lizard, Diploderum polygonatum polygonatum.

As the common name suggests, it is a native subspecies on Okinawa and the Amami Islands, where the Ryukyu Nature Positive is based, and the native distribution range of "the species" is limited to the Central Ryukyus and areas further south.

While it is known as one of the symbolic creatures of the Central Ryukyus, its population is said to have declined in recent years due to artificial habitat loss and the impact of invasive species.

On the other hand, it is truly ironic that remote populations were brought by artificial importation to Kyushu areas (including Yakushima Is.) and Shizuoka Pref. — are now being targeted for control as an invasive species that threatens local ecosystems.

Furthermore, issues surrounding domestic alien species, such as the Okinawa tree lizard and, like the Yaeyama firefly, involve significant challenges in institutional responses.

Species regulated under the Invasive Alien Species Act, which falls under the jurisdiction of the Ministry of the Environment, are those that have come from abroad.

Domestically derived invasive species fall outside the scope of the Invasive Alien Species Act regardless of the magnitude of their impact.

Even if responsible local governments designate them through ordinances, the reality is that they have limited budgets and personnel to implement countermeasures on their own, and the effectiveness of these measures varies widely...

The impact of human-induced organisms cannot be expected based on whether or not they crossed national borders.

My feeling is that the more natural endemism maintained among neighboring islands, the more caution is needed regarding the impact when artificial contamination occurs across those boundaries.

Rather than letting it get out of control and giving up once the situation becomes irreversible, we should use our imagination to take proactive measures from an early stage.

This is a crucial perspective for addressing invasive species, from the individual level all the way up to the government level.

I hope that by adopting this perspective, we can find ways to improve and implement the current system more effectively.

杉林があちこちに。沖縄とは違った風景です。There are cedar woods here and there. It is a different view from Okinawa.